Abstract
INTRODUCTION: Solid-basaloid adenoid cystic carcinoma (SB-AdCC) is a rare and aggressive variant of AdCC of the breast. Moreover, it is an extremely rare subtype of triple-negative breast cancer, accounting for <1% of all breast cancers. We report a case of SB-AdCC. CASE PRESENTATION: Ten years ago, an 82-year-old woman underwent a partial mastectomy for the luminal HER2 (human epidermal growth factor receptor type 2)-type invasive ductal carcinoma of the left breast cancer. Ten years later, she noticed another lump in her left breast. A needle biopsy was performed, and an unclassified carcinoma was detected. Histological examination revealed that the carcinoma was of the triple-negative type. A mastectomy of the left breast and sentinel lymph node biopsy were performed. The postoperative pathological diagnosis was an SB-AdCC of the breast. The Ki-67 index was 80%, corresponding to a high-grade malignancy. She received postoperative chemotherapy with tegafur-gimeracil-oteracil potassium. At 1 year postoperatively, she is recovering well without signs of metastasis. CONCLUSIONS: We reported a case of SB-AdCC.